package qunar.tc.bistoury.instrument.client.spring.el;

import java.util.List;

/**
 * Expressions are executed in an evaluation context. It is in this context that
 * references are resolved when encountered during expression evaluation.
 *
 * <p>There is a default implementation of the EvaluationContext,
 * {@link org.springframework.expression.spel.support.StandardEvaluationContext} that can
 * be extended, rather than having to implement everything.
 *
 * @author Andy Clement
 * @author Juergen Hoeller
 * @since 3.0
 */
public interface EvaluationContext {

	/**
     * Return the default root context object against which unqualified
	 * properties/methods/etc should be resolved. This can be overridden
	 * when evaluating an expression.
	 */
	TypedValue getRootObject();

	/**
	 * Return a list of resolvers that will be asked in turn to locate a constructor.
	 */
	List<ConstructorResolver> getConstructorResolvers();

	/**
	 * Return a list of resolvers that will be asked in turn to locate a method.
	 */
	List<MethodResolver> getMethodResolvers();

	/**
	 * Return a list of accessors that will be asked in turn to read/write a property.
	 */
	List<PropertyAccessor> getPropertyAccessors();

	/**
	 * Return a type locator that can be used to find types, either by short or
	 * fully qualified name.
	 */
	TypeLocator getTypeLocator();

	/**
	 * Return a type converter that can convert (or coerce) a value from one type to another.
	 */
	TypeConverter getTypeConverter();

	/**
	 * Return a type comparator for comparing pairs of objects for equality.
	 */
	TypeComparator getTypeComparator();

	/**
	 * Return an operator overloader that may support mathematical operations
	 * between more than the standard set of types.
	 */
	OperatorOverloader getOperatorOverloader();

	/**
	 * Return a bean resolver that can look up beans by name.
	 */
	BeanResolver getBeanResolver();

	/**
	 * Set a named variable within this evaluation context to a specified value.
	 * @param name variable to set
	 * @param value value to be placed in the variable
	 */
	void setVariable(String name, Object value);

	/**
	 * Look up a named variable within this evaluation context.
	 * @param name variable to lookup
	 * @return the value of the variable
	 */
	Object lookupVariable(String name);

}
